Everything You Need to Know About the Pfizer Vaccine

In August 2021, the Food and Drug Administration (FDA) formally approved a COVID-19 vaccine made by the drug manufacturers Pfizer and BioNTech to protect people ages 16 and older. Marketed as Comirnaty, the Pfizer-BioNTech vaccine was the first to be fully green-lit by the FDA to prevent COVID-19.

Children ages 6 months to 15 can now receive the Pfizer vaccine under an emergency use authorization (EUA) granted by the FDA. Two other vaccines are now available in the U.S., the Johnson & Johnson (J&J) and Moderna COVID-19 vaccines.

The Moderna vaccine is similar to the Pfizer formulation, highly effective, and available for people ages 6 months and older. The J&J vaccine is authorized for those 18 and older but is only recommended for specific populations due to safety and efficacy concerns.

As of December 1, 2022, over 390 million shots of the Pfizer vaccine have been given, making it the most commonly administered COVID-19 vaccine in the U.S. Here's what you need to know about how safe and effective the Pfizer vaccine is, and what makes it different from other immunization options.

All About the Pfizer COVID-19 Vaccine

The Pfizer vaccine comes in the form of two injections, given three to eight weeks apart. Children 6 months to 4 years old also get a third dose as part of the primary series. All fully vaccinated individuals ages 5 and older should also get a bivalent booster dose. Kids under 5 who have completed the primary series with Pfizer don't need a booster, but those who have only gotten one or two primary shots will get the bivalent dose as their third primary shot.

Five-year-olds must get a Pfizer bivalent booster. People who are 6 and older can get a booster dose of any of the FDA-authorized vaccines. It does not matter which vaccine brand was used for the primary series. The Pfizer or Moderna booster shots are preferred.

People can have one FDA-approved vaccine brand for their primary series and a different one for the booster. "Mixing and matching" brands is fine, although the Moderna booster is for kids 6 and up, while the Pfizer booster is for ages 5 and up. Children ages 5 and up who received the Pfizer vaccine are eligible to get a bivalent booster shot two months after completing their primary series.

The Pfizer COVID-19 vaccine comes from research conducted on other strains of coronaviruses. This class of viruses is characterized by spikes that resemble a crown.

Pfizer uses mRNA technology in its vaccine, a new laboratory-made formulation that carries instructions for our cells to make a harmless piece of the protein mimicking the spikes. This in turn triggers our bodies' immune system to fight the real virus when it enters the body. The Moderna vaccine uses similar technology.

According to Jason G. Newland, MD, MEd, professor of pediatrics at Washington University’s St. Louis Children’s Hospital, “Previous research has allowed us to understand what parts of the virus are important in its life cycle and for our bodies to make antibodies to prevent us from getting sick. The Pfizer vaccine was based on studies that were done on previous coronaviruses recognizing that the spike protein is part of the keys to our bodies producing antibodies.”

Is the Pfizer Vaccine Safe?

The Pfizer vaccine is safe and effective. The FDA's authorization and approval of the Pfizer vaccine came after scientists reviewed months of data on how people reacted in preclinical and clinical trials, as well as additional detailed information submitted by the pharmaceutical maker about how and where the vaccine is manufactured and administered.

To date, the Pfizer vaccine has been very well-received by a wide range of people, with few side effects. The FDA's datasheet for the vaccine indicates it’s been tested on roughly 23,000 people ages 12 and older in clinical trials and “has been shown to prevent COVID-19" following two doses, given three weeks apart. It's also been rigorously tested in babies and young children ages 6 months to 11 years old.

In February 2022, the CDC added interim clinical considerations for extending the interval between the primary doses of mRNA vaccination (including Pfizer) for those 12 and over to 8 weeks rather than the original recommendation of a 4-week interval. This change is due to the very small risk to adolescents of developing myocarditis after getting the vaccine. Some studies have shown that spacing out the second shot reduces this risk while also offering increased vaccine efficacy.

Pfizer CEO Albert Bourla has said that the Pfizer vaccine will likely need to be taken annually, similar to the flu shot. A lot of the logistics depend on how much the COVID-19 variants evolve and spread. Despite that, “vaccine efficacy is 94% to 95%, which is extremely high,” says Dr. Newland.

Additionally, preliminary research suggests that getting a third dose of Pfizer offers better protection against the Omicron and other variants than just two doses.

Risks of the Pfizer COVID-19 Vaccine

Scientists at the CDC and the FDA are reviewing reports of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation in the lining of the heart) in people who've received the Pfizer or Moderna vaccines. These very rare cases usually occur after the second dose and are more common in teen boys and young adult males. Symptoms include a fluttering heart or shortness of breath.

Still, the CDC says the benefits of vaccination outweigh the known and possible risks, including myocarditis and pericarditis. Most people with these conditions recover quickly in response to medication and rest.

Side Effects

Side effects of the Pfizer vaccine have been minimal during clinical trials. They include:

• Chills
• Fatigue
• Feeling unwell
• Fever
• Headache
  
• Injection site swelling or redness
• Joint pain
• Muscle pain
• Nausea
• Pain at the injection site
  
• Swollen lymph nodes (lymphadenopathy) 

Who Should Not Get the Vaccine

You should not get the vaccine if you’ve had an immediate allergic reaction (even if not severe) to any ingredients in an mRNA COVID-19 vaccine or PEG and polysorbate. For these individuals, the J&J vaccine may be recommended instead.

The CDC says the vaccine is safe for those with a history of severe allergic reactions, including food, pet, venom, environmental, or latex allergies. However, these individuals should be monitored for 30 minutes after receiving the injection.  

Can Pregnant People Get the Pfizer COVID-19 Vaccine?

According to the latest recommendations from the nation's leading health organizations, including the CDC and the American College of Obstetricians and Gynecologists (ACOG), all pregnant people should be vaccinated against COVID-19.

Pregnant people were not included in early clinical trials of the Pfizer vaccine. But a study of 35,691 people who were pregnant between December 14, 2020, and February 28, 2021, found that mRNA vaccines, including Pfizer, do not appear to have any serious risks.

Pfizer launched a clinical trial on how safe and effective the vaccine is in pregnant women, specifically. According to experts, it's especially important that pregnant people get vaccinated because they sometimes have more severe cases of COVID-19 than their non-pregnant counterparts.

According to the ACOG statement, available data suggest that symptomatic pregnant patients with COVID-19 are at increased risk of more severe illness compared with non-pregnant peers. If you are pregnant, discuss vaccine risks and benefits with your doctor.

Can Kids Get the Pfizer COVID-19 Vaccine?

While only formally approved for use in people ages 12 or older, the FDA has now authorized Pfizer’s COVID-19 vaccine for use in kids ages 6 months and up. The American Academy of Pediatrics (AAP) and CDC have recommended that all children ages 6 months and older get the vaccine as soon as possible.

Pfizer has conducted clinical trials to study the vaccine in children younger than 12. The company data shows that it produces a strong immune response and only mild side effects in kids ages 5 to 11.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.